Vacuum cleaner heads typically comprise longitudinal extending casings having a dirty air inlet extending transveresly across the front thereof. An agitator to assist in entraining dirt in the air flow stream (such as a rotatably mounted brush) may be mounted above the dirty air inlet.
A rotatably mounted brush assists in cleaning a surface such as a carpet or rug. As the brush rotates, it agitates the fibres of the carpet thus disturbing the dirt and assisting the entrainment of the dirt in the air stream entering the dirty air inlet. However, the rotation of the brush may scratch or otherwise mar a bare floor, such as a wood floor, linoleum or the like. Therefore, it has been known in vacuum cleaners to include a height adjustment means to raise the brush so as to remove it from contact with the surface when the vacuum cleaner is in a bare floor cleaning mode. Alternately, it has been known to interrupt the rotation of the brush when the vacuum cleaner is in the bare floor cleaning mode. In either case, the agitation created by the rotation of the brush is not available to assist in cleaning when the vacuum cleaner is in the bare floor cleaning mode.
U.S. Pat. No. 2,930,069 (Kowalewski) discloses a turbine driven power head which has a flexible vertical wall which is positioned behind a rotating brush. The flexible vertical wall has fingers which contact the surface over which the vacuum cleaner is passed so as to cause the wall to move in the opposite direction to the direction of travel of the vacuum cleaner head. This is used to balance the load on the turbine during the travel of the vacuum cleaner head forward and rearward across the surface.
U.S. Pat. No. 3,936,905 (Stewart et al) discloses a vacuum cleaner suction tool which has a hand operated control knob for decreasing the size of the dirty air inlet at the option of the user.
U.S. Pat. No. 2,219,802 (Bjorkman) discloses a suction nozzle which does not contain a rotating brush. In one embodiment, the suction nozzle has two inlets, one of which is larger than the other. A valve is moved to sequentially connect the smaller and the larger openings. In an alternate embodiment, the vacuum cleaner has a single dirty air inlet. An inlet to the air flow path through the vacuum cleaner head is positioned distal to the dirty air inlet. A valve is provided with the entrance to the air flow path so as to change the size of the entrance.